Among hospital intensive care units (ICUs) with a daytime physician specially trained in critical care, adding a specialist to cover the night shift does not improve patients' survival, according to a new study. Among hospitals with ICUs that don't have a dedicated critical care physician during the day, however, the presence of such a doctor at night was tied to a smaller likelihood that patients would die. The results, published in the New England Journal of Medicine, counter an argument from some in the medical community that ICUs need round-the-clock intensivists—doctors who specialize in critical care.